Fine particles of crosslinked fluorine-containing elastomer (hereinafter also referred to as “crosslinked fluorine-containing elastomer fine particles”) are used for the purpose of imparting flexibility, etc., for example, to various synthetic resins, especially thermoplastic fluorine-containing resins.
For preparing such crosslinked fluorine-containing elastomer fine particles, there are known (1) a method of pulverizing crosslinked fluorine-containing elastomer particles, (2) a method of preparing fluorine-containing elastomer fine particles by emulsion polymerization in the presence of a monomer having two or more ethylenically unsaturated groups as a copolymerizable component, thereby simultaneously crosslinking with the advance of the polymerization, and (3) a method of impregnating fluorine-containing elastomer fine particles prepared by emulsion polymerization with a vulcanizing agent and a vulcanization aid and then vulcanizing the fine particles in the form of latex (JP6-248146A and JP8-59941A).
However, in the case of the finely pulverizing method (1), there is a problem that a particle size of the crosslinked fluorine-containing elastomer particles becomes large.
Also in the method (2) of carrying out crosslinking simultaneously during polymerization, there is a problem that since polymerization reaction is inhibited by crosslinking reaction, a molecular weight is not increased and sufficient strength is not obtained.
Further, with respect to the method (3) of vulcanizing emulsified polymer particles in the form of latex, JP6-248146A and JP8-59941A do not disclose concrete means for vulcanizing emulsified polymer particles in the form of latex. It is only the method (2) of carrying out crosslinking simultaneously during polymerization that is concretely disclosed in JP6-248146A and JP8-59941A.